Hamstring injuries are one of the most common issues in sports, affecting athletes from various disciplines such as football, athletics, and rugby. These injuries not only come with high economic and personal costs for the athletes, but they also severely impact performance. One of the main factors contributing to these injuries is the imbalance of strength between the hamstrings and quadriceps, as well as alterations in sprint mechanics, which are often not properly assessed. Through understanding an athlete’s force-velocity profile, coaches and physiotherapists can design more effective prevention strategies and more specific rehabilitation protocols.

The Impact of Hamstring Injuries

Hamstring injuries are characterized by pain in the back of the thigh, which can range from a mild strain to a severe muscle tear. These injuries are particularly common in sports that require sprints, rapid changes of direction, and jumping. One key aspect of these injuries is their high recurrence rate. Athletes who have sustained a hamstring injury are significantly more likely to suffer another injury, especially if the factors contributing to the initial injury are not adequately addressed.

The consequences of a hamstring injury go beyond the immediate discomfort and the inability to perform at the highest level. These injuries can shorten an athlete’s career and generate a significant economic cost for sports clubs due to long recovery periods and treatment. Hence, it is essential to develop preventive approaches that not only help avoid injuries but also facilitate more efficient rehabilitation and a safe reintegration into training and competition.

The Force-Velocity Profile: A Key Tool for Prevention

One of the main strategies for preventing hamstring injuries lies in analyzing the athlete’s force-velocity (F-V) profile. This profile measures the relationship between the athlete’s ability to generate force and the speed at which they can maintain that force during a sprint. Traditionally, strength training has focused on increasing an athlete’s maximum strength, but the importance of the speed at which this force is applied during acceleration phases of the sprint has become an area of growing interest.

In a sprint, the ability to generate horizontal force in the early phases of acceleration is crucial. As an athlete increases their speed, the production of horizontal force (toward the ground) is essential for efficient acceleration. Sprint mechanics involve a complex interaction between the leg muscles, particularly the hamstrings, glutes, and quadriceps, which are responsible for hip extension and forward propulsion. However, it is often overlooked that it is not just maximum strength, but the ability to apply this force horizontally, that determines sprint performance and, therefore, injury risk.

The force-velocity profile not only measures an athlete’s maximum strength but also how that strength is distributed across different speeds. This approach allows for the identification of which aspects of an athlete’s sprint mechanics may need improvement, which in turn allows for the design of more specific training to enhance performance and reduce injuries.

Strength Imbalance: A Key Factor in Injury Risk

One of the most significant factors related to hamstring injuries is the strength imbalance between the hamstrings and quadriceps. The imbalance between these two muscle groups is a clear indicator of an increased risk of injury, especially in athletes who perform explosive movements such as sprints. The hamstrings play a fundamental role in decelerating and stabilizing the leg during the running cycle, while the quadriceps are responsible for knee extension. If the hamstrings are not strong enough relative to the quadriceps, this can lead to excessive strain on the hamstrings, increasing the likelihood of an injury.

In this regard, coaches and physiotherapists should focus on improving the strength ratio between these muscles, particularly in the eccentric phase, which occurs when the hamstrings stretch under load. Eccentric exercises, such as those mimicking the final phase of the sprint or eccentric squats, are essential for enhancing hamstring resilience and reducing injury risk.

The Importance of Horizontal Force in Sprinting

As athletes increase their speed in sprints, the activity of the hip extensors, including the glutes and hamstrings, becomes more significant. However, most existing studies have focused on constant speeds, meaning they examine an athlete’s maximum speed during a sprint. While this type of study has provided valuable insights, it does not directly address the issue of acceleration, where hamstring injuries are most likely to occur.

Acceleration is a critical component of sprinting, and it is during this phase that an athlete must generate enough horizontal force to propel themselves forward. In the early stages of the sprint, athletes need to produce significant horizontal force to accelerate efficiently. Studies have shown that athletes who are able to generate more horizontal force during the acceleration phase have a lower risk of hamstring injuries. This is particularly relevant for strength coaches and physiotherapists, as improving the ability to generate horizontal force can be a key factor in preventing these injuries.

The Use of the Force-Velocity Profile in Rehabilitation

The force-velocity profile is not only useful for injury prevention but also for rehabilitation. Physiotherapists can use this profile to monitor the recovery of athletes after a hamstring injury. By analyzing the force-velocity profile, it is possible to identify areas of weakness that need to be addressed during rehabilitation.

A key aspect is measuring the horizontal force (F0) during the early moments of the sprint. Athletes with a history of hamstring injuries often show a reduced capacity to generate this horizontal force in the early phases of the sprint, although they may recover their maximum speed over time. However, just because an athlete has reached their maximum speed does not mean they have fully returned to their previous level of performance. Continuous monitoring of the force-velocity profile allows physiotherapists and coaches to make informed decisions about the appropriate time to reintegrate the athlete into high-intensity training and competition.

Evaluating the Force-Velocity Profile

The evaluation of an athlete’s force-velocity profile can be carried out through various methods, ranging from the use of force plates to more accessible technologies like mobile applications. These applications allow precise measurements of horizontal force during the sprint using videos recorded at high speed. Although relatively new, such tools hold great potential for making force-velocity assessments more accessible to coaches and physiotherapists, which can enhance both performance and injury prevention.

These systems measure the speed at which an athlete reaches their maximum speed and the amount of force they are able to generate throughout the sprint. This data is then used to create a force-velocity profile, which can be used to personalize training and rehabilitation interventions. This way, strengths and weaknesses in each athlete can be identified, enabling the design of more effective and tailored training programs.

Injury Prevention and Rehabilitation: A Personalized Approach

The key to preventing and rehabilitating hamstring injuries lies in the individualization of training programs. Each athlete has a unique force-velocity profile that must be assessed and understood in order to design a training approach that suits their specific needs. This is especially important for athletes who have suffered a hamstring injury, as a personalized rehabilitation approach will not only speed up recovery but also reduce the likelihood of re-injury.

Strength coaches and physiotherapists must work together to ensure that athletes are regaining the strength needed to avoid injuries, as well as the ability to generate horizontal force efficiently during sprints. Furthermore, the use of technologies to measure the force-velocity profile allows for continuous monitoring of the athlete’s progress and the adjustment of training accordingly.

Conclusion

Hamstring injuries present a complex challenge in sports, but the analysis of the force-velocity profile provides a powerful tool for both prevention and rehabilitation. By understanding how an athlete generates force throughout the sprint and how that force is distributed across different speeds, coaches and physiotherapists can design more specific training programs, improve sprint mechanics, and reduce injury risk. Additionally, by using these tools to assess and monitor progress during rehabilitation, it is possible to ensure that athletes fully recover before rejoining competition.